1. Field of the Invention
The present invention relates to an image display apparatus such as a projector or a monitor.
2. Description of the Related Art
An image signal (image data) having a high resolution may be inputted to an image display apparatus. In this case, the capacity of the image data is enlarged. If the capacity of a frame buffer provided in the image display apparatus increases or the access speed for the frame buffer speeds up in order to cope with the image data having the large amount of capacity, the cost is increased. Therefore, the technology of reducing the capacity of the image data written in the frame buffer by compressing the image data is widely used.
The compression processing is preferably performed by using a simple method such as a bit shift method in view of costs, but such a compression method causes a deterioration of an image quality since it is a lossy color (gradation) compression processing. Therefore, a case where the lossy color compression processing is applied needs to be limited.
For example, Japanese Patent Laid-Open No. 2007-72360 discloses an image display apparatus that switches the application and the non-application of the lossy color compression processing in accordance with whether a keystone adjustment is effective or ineffective in order to limit the case where the lossy color compression processing is applied.
However, in the image display apparatus disclosed in Japanese Patent Laid-Open No. 2007-72360, the disturbance of the image generated at the time of switching the application and the non-application of the lossy color compression processing such as a bit shift needs to be concealed. Therefore, it cannot be used in a case where the switching the application and the non-application of the lossy color compression processing is frequently performed.